UA111241C2 - A METHOD FOR PREPARING HIGH CLEANING CRYSTAL CARBAMIDE - Google Patents

Abstract

The invention relates to a method of obtaining crystalline urea high purification. A method is proposed, which involves crystallization of urea and its drying, with the aqueous solution of urea preheated from to, after which the solution is subjected to electrodialysis purification at a voltage of 400 V-600 V. The technical result is to obtain crystalline urea of high purity, allowing to use it as an additive in the food industry and as a reagent in laboratory analyzes.

Description

Description

The invention relates to the field of obtaining urea, in particular to the method of obtaining highly purified urea.

Currently, the methods of obtaining granular and crystalline urea are widely known.

Industrial methods of obtaining urea are based on the crystallization of an aqueous solution of urea obtained from carbon dioxide and ammonia. However, urea obtained by known methods does not have a sufficient degree of purity for use in the food industry and for use as a reagent in laboratory analyses.

The closest technical solution chosen as a prototype is the method of obtaining crystalline urea obtained on the basis of carbon dioxide and ammonia (patent KO 2041202).

The method includes crystallization of urea in the entire volume of the saturated solution, squeezing of the crystals until a compact mass is obtained, followed by the removal of urea crystals by filtration and their drying. However, the obtained urea also does not have a sufficient degree of purity for use in the food industry and for use as a reagent in laboratory analyses.

The technical objective of the claimed invention is to obtain crystalline urea of high purity.

The task is achieved by the fact that in the method of obtaining high-purity crystalline urea from an aqueous solution of urea, which includes crystallization of urea and its drying, according to the invention, the aqueous solution of urea is preheated from -30 "C to 130 "C, after which the solution is subjected to electrodialysis cleaning at a current voltage of 400 V - 600 V. At the same time, at 30 95 concentration of the solution, it is heated to "30 "C, at a concentration of 50 95 - to 40-50 "C, at a concentration of 70 95 - to 70-80 "C, at concentrations of 90 Fo and higher - up to -90-130 "C.

The device for the implementation of the claimed method is shown in Fig.1. The device contains storage tank 1 for the original urea solution, electrodialysis apparatus 2, pump C for supplying the solution from tank 1 to electrodialysis apparatus 2, tank 4 for purified urea solution, pump 5 for supplying purified urea solution to tank 4, crystallizer-evaporator 6, pump 7 for supplying purified urea from container 4 to crystallizer-evaporator 6.

The method is carried out as follows. The crude aqueous solution of urea in the storage tank 1 is heated to the operating temperature from 30 "C to -130 "C in order to exclude premature crystallization of urea. At the same time, when the concentration of the solution is 30 95, it is heated to "30 "C, when the concentration is 50 95 - to 40-50 "C, at 70 Fo - to 70-80 "C, when 90 95 and above - to "590-130 " WITH. The dependence of the concentration of the solution and its heating temperature was determined empirically and is presented in Table 1.

Table 1, curve of crystallization of urea in water

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As can be seen from Table 1, when the temperature of the urea solution is less than 30 °C, urea partially enters the crystalline state. When the solution is heated above 130 °C, partial hydrolysis of urea occurs, as well as its dimerization to biuret, the content of which in the purified urea is strictly standardized.

Next, the solution enters the electrodialysis apparatus 2 with the help of the pump C. In the electrodialysis apparatus 2, salt-forming ions are removed from the solution under the action of an electric current with a voltage of 400 V - 600 V. This range provides the optimal mode of process productivity: the quantity/quality ratio. At a current intensity higher than 600 V, the resulting product does not meet the requirements for purified urea, which is used in laboratory analyzes and in the food industry. At a current below 400 V, the electrodialysis cleaning process is slow, which reduces the productivity of the process. After the deionization process, the purified solution is fed into the storage tank 4 with the help of pump 5, and then with the help of pump 7 - into the crystallizer - evaporator 6, where the solution is separated into purified crystalline urea (crystallization of urea) and deionized water. Crystallization of urea with its simultaneous drying takes place by heating the solution to 110 "C-150 C at atmospheric pressure or at a vacuum pressure of 50-10 mm Hg. 50-80 70.

The quality indicators of urea obtained using the claimed method are presented in Table 2.

Table 2 is more

Thus, the degree of purity of the obtained crystalline urea allows its use as an additive in the food industry (food additive E927B) and as a reagent in laboratory analyses.

Next, the obtained crystalline urea of high purity is packed in polypropylene bags or other similar containers. The obtained deionized water is a by-product with a target application: use as a component of antifreeze and antifreeze liquid for car windshield washers.

Claims (2)

FORMULA OF THE INVENTION 1. The method of obtaining highly purified crystalline urea from an aqueous solution of urea, which includes crystallization of urea and its drying, which is characterized by the fact that the aqueous solution of urea is preheated from 30 "C to 130 "C, after which the solution is subjected to electrodialysis purification at a voltage of 400 V-600 V. 2. The method according to claim 1, which differs in that at a concentration of 30 95% of an aqueous solution of urea, it is heated to 30 "C, at a concentration of 50 95 - to 40-50 "C, at a concentration of 70 95 - to 70-80 "C, with a concentration of 90-95 and above - up to 90-130 "C. WE 7 и и 1 Ни тво . и Й N Deionized water f 1 tini ik pin, tini nih io ik chigini between my skin» kyu xx yuyu 1 8 2 : zh Z m 5 | 7 lyane zhnantnyaya I Crystallized urea Fik.i pact tt t veto t mete mk ton totyatoteoj